The present invention is generally related to reducing power consumption of a host digital device and, more particularly, to a control arrangement and associated technique used in a component that interfaces with the host device and limits power consumption of the component.
There is an ongoing desire to reduce power consumption in portable electronic units such as, for example, those units that employ digital technology. As functional capability of such portable units is enhanced over time and in view of another ongoing desire for miniaturization, the need for reducing power consumption may be brought into even further focus. Further, there is an ongoing need to provide for increased amounts of data storage in portable units. One approach, that is being used to satisfy this latter need, is the use of miniature hard disk drives. Such a miniature hard disk drive, however, is representative of a class of portable device components that can consume a significant amount of electrical power. Thus, power saving features, as applied to the use of a hard disk drive, are generally of interest with respect to the present discussion.
The prior art contains a number of examples which attempt to save power in the context of portable use of a hard disk drive. One approach, which is likewise applied even in the use of a hard drive in a desktop host computer, is to use the host computer to signal the hard drive to power down when the drive is not needed. This approach, however, requires monitoring and host resources to power down and wake up the drive. A related approach uses a timer in the hard drive to cause the drive to power down, should the timer time out prior to the hard drive becoming engaged in a data transfer. One concern, with respect to the use of a timer, relates to selection of an appropriate time out period. If the selected time out period is too short, the drive will often be re-started, which can itself consume additional power. Likewise, if the selected period is too long, power will be consumed without engaging in data transfers. The selection of this time period can be difficult when data transfers are often of different sizes and/or frequency.
Another class of prior art approach attempts to provide power savings during the actual operation of the drive. One instance of this latter type of approach is seen in U.S. Pat. No. 5,402,400, issued to Shrinkle et al (hereinafter the Shrinkle patent). The Shrinkle patent attempts to take advantage of the fact that there are times when a control system need only monitor servo information during operation of the drive for purposes of track following. Since the servo information occurs intermittently as servo sectors or wedges pass under the read heads, at least certain portions of the control circuitry can be shut down between the servo sectors, when the drive is not engaged in a read or write operation. This approach, however, is limited to power savings only during actual operation of the drive. Power savings may not be significant if data transfers occur only intermittently and are performed at relatively high data rates, in view of the amount of data that is being transferred.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.